Nervous System Flashcards

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1
Q

What are the 2 main parts of the nervous system?

A

CNS, brain and spinal cord.
PNS, somatic and autonomic nervous system.

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2
Q

What is a stimulus and what does it produce?

A

It is a detectable change in the internal/external environment of an organism that produces a response.

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3
Q

What are the elements of a reflex arc?

A

Stimulus.
Receptor.
Sensory neurones.
Relay neurone in CNS.
Motor neurone.
Effector.
Response.

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4
Q

What are the 3 types of neurone?

A

Sensory.
Motor.
Relay.

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5
Q

What is happening when the axon membrane is at resting potential and what value is this?

A

Sodium and potassium gated channels are closed and the Sodium Potassium co-transporter protein is actively transporting 3 sodium out and 2 Potassium in. Some K+ channels are open/leaky so some K+ diffuses back out. The resting potential is -70mV.

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6
Q

How is an action potential initiated?

A

By depolarising the membrane. The energy of the stimulus causes the voltage gated sodium channels to open allowing to rapidly diffuse into the axon, down their concentration gradient. Axon becomes 40mV.

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7
Q

What happens after the axon is depolarised?

A

Its repolarised. The sodium channels close and the Potassium voltage gated channels open and Potassium diffuse down their concentration gradient. However, more diffuse out than Na+ diffused in which makes the membrane hyperpolarised.

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8
Q

How is the axon membrane restored to resting potential after hyperpolarisation?

A

The potassium channels close, the sodium-potassium pump pump K+ ions back in and Na+ ions back out, restoring the ion balance.

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9
Q

How does the action potential travel along an axon?

A

As Na+ ions move laterally through the axon, they depolarise the adjacent section of the membrane, opening more voltage gated channels.

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10
Q

What is the absolute refractory period and what does it ensure?

A

It is the period during which no new action potential may be initiated. It prevents the action potential being propagated back in the direction from which it came.

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11
Q

What is the stimuli threshold?

A

Where a nervous impulse is either initiated or not and its always the same size. It prevents minor stimuli from setting up nervous impulses, so the brain isn’t overloaded with information.

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12
Q

How does the brain detect how strong a stimulus is all the action potentials are the same size?

A

Due to the frequency of them.

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13
Q

What factors affect the speed of conduction of the nerve impulse?

A

Temperature.
The diameter of the axon.
Myelination.

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14
Q

What is saltatory conduction?

A

Transmission of a nerve impulse along a mylelinated axon, in which the action potential jumps from one node of ranvier to the adjacent node.

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15
Q

In a chemical synapse, what is the impulse transmitted by?

A

Neurotransmitter.

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16
Q

What happens during synaptic transmission?

A

The arrival of an impulse opens voltage gated Ca+ channels and they diffuse in.

Influx of Ca+ causes synaptic vesicles to move to and fuse with the membrane, releasing acetylcholine into synaptic cleft.

Neurotransmitter binds to a receptor which causes the membrane to depolarise, thus initiating another action potential.

17
Q

Why do neurones only transmit impulses in one direction?

A

Repolarisation happens behind an action potential so depolarisation couldn’t happen at this point.

Synaptic vesicles only occur at the bulb of the pre-synaptic neurone.

Neurotransmitter receptors only occur on the post-synaptic membrane.

18
Q

What are the properties of synapses?

A

Transmit information between neurones.

Pass impulses in one direction only.

Act as junctions.

Protect the response system from overstimulation.

Filter out low level-level stimuli (Action potential only initiated when depolarisation is large enough to reach a threshold value.

19
Q

What are the 2 different effects drugs can have on synapses?

A

Sedatives, fewer action potentials in post-synaptic neurones.

Stimulants, allowing more action potentials in post-synaptic neurones.

20
Q

What are the 2 main mechanisms that drugs act?

A

They may mimic the action of the neurotransmitters (E.g. nicotine and acetylcholine).

Drugs may prevent Calcium ions diffusing into the pre-synaptic membrane